1. Field of the Invention
The present invention relates to a pallet-clamping device used for a machine tool such as a machining center. More particularly, the present invention relates to a pallet-clamping device for manually carrying out the operations of positioning and clamping a work pallet to a work table of a machine tool.
2. Description of the Related Art
In a machine tool provided with a work table, such as a machining center, a pallet-clamping device for positioning and fixing a work pallet to the work table has been recently used together with a pallet-changing device for changing a work pallet on the pallet-clamping device. An ordinary pallet-clamping device comprises a base block secured to a work table of a machining center or the like, a positioning unit for positioning a work pallet relative to the base block, and a clamping unit for clamping the work pallet to the base block, and these positioning and clamping units are automatically operated by an actuator driven by a drive source such as a hydraulic pressure, pneumatic pressure, or electric power.
In this automatic pallet-clamping device, a work pallet delivered onto the pallet-clamping device can be automatically positioned and fixed, and therefore, this automatic pallet-clamping device can carry out a very efficient exchange of work pallets between the pallet-changing device and the machining center or the like. This type of pallet-clamping device, however, is expensive, and is disadvantageous in that careful maintenance is necessary. When the pallet-clamping device is attached to the already existing machining center or the like, complicated wiring work must be carried out and thus the cost is increased. Moreover, since a hydraulic pressure-generating device, a pneumatic pressure-generating device or the like must be provided, it is often difficult to later install such a device in a relatively small-sized factory.
To eliminate these disadvantages, a method may be considered in which the respective units of the pallet-clamping device are manually operated. In this case, however, the operation becomes complicated and a failure to perform a certain operation can result in an accident. Furthermore, when a work pallet is manually delivered onto the pallet-clamping device, if the delivery force is too strong, a return or rebound of the work pallet occurs and the subsequent clamping operation or positioning operation often becomes difficult.